Aircraft flight control

ABSTRACT

An aircraft flight control ( 10 ) includes a control stick ( 11 ) with a handle ( 14 ) and a root ( 13 ) that are interconnected by an intermediate segment ( 12 ) of the control stick ( 11 ). The flight control ( 10 ) includes a pitch shaft ( 20 ) and a roll shaft ( 30 ) that are mutually perpendicular, the control stick ( 11 ) passing through an oblong orifice ( 21 ) formed in the pitch shaft ( 20 ), the root ( 13 ) being mechanically connected to the roll shaft ( 30 ) by a mechanical connection ( 40 ), while the intermediate segment ( 12 ) is connected to the pitch shaft ( 20 ) via a connection pin ( 70 ) that passes through the intermediate segment ( 12 ) and that is arranged axially in the oblong orifice ( 21 ).

FIELD OF THE INVENTION

The present invention relates to a flight control for an aircraft, inparticular for a helicopter.

BACKGROUND OF THE INVENTION

Conventionally, the flight controls of an aircraft include a controlstick.

The control stick is then connected to flight control members of theaircraft via a control line that may be mechanical, or electrical inmodern aircraft. By moving the control stick from front to back and fromleft to right, the pilot can control the aircraft being piloted.

More particularly, a helicopter has a main lift and propulsion rotorthat has a plurality of blades.

By adjusting collectively and identically the pitch of the blades, thepilot varies the magnitude of the overall lift of the main rotor so asto control the altitude and the speed of the helicopter. The pilotperforms this action with the help of a collective flight controlimplementing a pitch lever that is commonly referred to as the“collective pitch lever”.

In contrast, by controlling the cyclical variation of the pitch of theblades with the cyclical flight control stick, which stick is referredto below as the “control stick”, the pilot controls the attitude of theaircraft and its movement in translation.

As a result, helicopters are generally provided with a swash platecomprising a rotary plate and a non-rotary plate. The rotary plate isconnected to the blade via pitch levers, while the non-rotary blade isconnected to servo-controls that are themselves controlled by thepilot's flight controls via electrical or mechanical transmission means.

By moving the control stick from front to back, the helicopter pilotcontrols in pitching the helicopter. And likewise, by moving the controlstick from left to right, the pilot controls the roll of the helicopter.

It can be understood that the controls need to be precise in order toavoid leading to incidents.

Unfortunately, with certain prior flight controls, coupling is observedto appear between the pitch and roll controls. Specifically, by movingthe control stick forwards, for example, it is found that the pilotmodifies both pitch and roll simultaneously as a result of the dynamicsof the control stick.

Document EP 0 522 623 discloses a flight control provided with a pitchand roll control stick suitable for avoiding the above-specifiedcoupling phenomenon.

The bottom end of the control stick is hinged to a support that isfastened to the floor of the aircraft. In addition, a roll control rodis hinged to a projection secured to said bottom end.

Furthermore, a pitch control rod is mechanically connected to anintermediate segment of the control stick via first and second cranks.

More precisely, the pitch control line comprises in succession: thecontrol stick, the first crank, the second crank, and then the pitchcontrol rod.

The device described in that document EP 0 522 623 suggests isolatingthe pitch and roll controls in order to solve the problem.

Nevertheless, it is found that the device is bulky, with the pilotfacing different flight control members.

OBJECT AND BRIEF SUMMARY OF THE INVENTION

An object of the present invention is thus to propose flight controlsthat are compact, having a control stick that does not run any risk ofgenerating the above-mentioned coupling phenomenon.

According to the invention, a flight control for an aircraft, moreparticularly for a helicopter, comprises a pitch and roll control sticksuitable for being turned about an axis dedicated to pitch, referred tofor convenience below as the pitch axis, and about an axis dedicated toroll, referred to below for convenience as the roll axis, the pitch androll axes being mutually perpendicular, and the control stick beingprovided with a handle and a root that are interconnected by anintermediate segment of the control stick.

The flight control is remarkable in that it includes a pitch shaft and aroll shaft that are mutually perpendicular for controlling the aircraftin pitching and rolling by performing rotary movements respectivelyabout the pitch axis and about the roll axis under drive from thecontrol stick, the control stick also passing through an oblong orificeformed in the pitch shaft, and the root of the control stick beingmechanically connected to the roll shaft by a mechanical connectionwhile the intermediate segment is connected to the pitch shaft via aconnection pin that passes through the intermediate segment and that isarranged axially in the oblong orifice on the roll axis.

Consequently, this compact flight control enables pitching and rollingto be decoupled.

When the pilot moves the control stick to pivot about the roll axis, thecontrol stick turns about its connection pin, the connection pin beingconstituted for example by a bar having its longitudinal axis ofsymmetry coinciding with the roll axis. Consequently, the root of thecontrol stick acts on the mechanical connection which in turn entrainsthe roll shaft to turn about said roll axis.

Furthermore, in the oblong orifice of the pitch shaft, the control stickcan move only from left to right or from right to left, and thereforedoes not entrain the pitch shaft.

In contrast, when the pilot moves the control stick so that it pivotsabout the pitch axis, the control stick cannot turn about the connectionpin, but instead pushes the connection pin and entrains turning movementof the pitch shaft about the pitch axis.

Furthermore, the mechanical connection does not cause the roll shaft tomove.

The pitch and roll controls are therefore completely decoupled.

In order to optimize compactness, the flight control includes a mainanchor platform anchoring it to the aircraft, the pitch and roll shaftsoptionally being fastened to the main anchor platform in such a manneras to perform turning movements respectively about the pitch and rollaxes.

More precisely, the pitch and roll shafts have respective first andsecond ends, the first and second ends of the roll shaft being fastenedrespectively to the structure of the aircraft and to a first side faceof the main anchor platform via hinges allowing said roll shaft to turnabout the roll axis.

Likewise, the first end of the pitch shaft is fastened to the structureof the aircraft by a hinge allowing said pitch shaft to turn about thepitch axis, while the second end of the pitch shaft passes through asecond side face of the main anchor platform, said first and second sidefaces being mutually perpendicular.

In addition, in order to enable the flight controls to act on the flightcontrol members of the aircraft, the control includes at least oneprimary rod hinged to a primary projection fastened to the pitch shaft.

The primary rod can then be connected to the flight control members viaa mechanical linkage.

Nevertheless, it is possible for the aircraft to include electric flightcontrols. Thus, the flight control can comprise at least one primarysensor for sensing the position of the pitch shaft, this primary sensoroptionally being controlled by the primary rod.

The flight control members of the aircraft are actuated depending on theposition of the pitch shaft as measured by the sensor. For example, in ahelicopter, the sensor delivers a signal relating to said position ofthe pitch shaft to a control member that acts on servo-controls formodifying the pitch of the blades of the main rotor of the helicopter.

Similarly, the flight control may include at least one secondary rodhinged to a secondary projection fastened to the roll shaft and/or to atleast one secondary sensor for sensing the position of said pitch shaft.

Furthermore, the mechanical connection advantageously includes a compasslinkage provided with first and second branches, the first branch of thecompass linkage being hinged to the root of the control stick and to afirst end zone of the second branch.

In a first variant of the invention, a second end zone of the secondbranch of the compass linkage is hinged to the roll shaft.

Consequently, by pivoting about the connection pin, and thus about theroll axis, the root of the control stick entrains in its movement thefirst and second branches of the compass linkage, and consequentlyentrains the roll shaft.

In contrast, by pivoting about the pitch axis, the root of the controlstick pushes or pulls the first branch. The compass linkage then tendsto open or close but does not give rise to any turning movement of theroll shaft.

In a second variant, the second end zone of the second branch of thecompass linkage is mechanically connected to the roll shaft via transfermeans comprising in succession a horizontal first transfer rod, avertical transfer member, and then a horizontal second transfer rod, aball-joint possessing a large amount of freedom to move angularlyallowing maximum angular movement of plus or minus 20° being locatedbetween the second branch of the compass linkage and the first transferrod of the transfer means.

By pivoting about the connection pin, and thus about the roll axis, theroot of the control stick entrains in its movement the first and secondbranches of the compass linkage, and consequently entrains the firsttransfer rod.

The vertical transfer member then acts on the second transfer rod sothat the second transfer rod moves in the direction opposite to thedirection of movement of the first transfer rod. The second transfer rodacts on the roll shaft that then moves in the same direction of rotationas the control stick about the roll axis.

It should be observed that the first branch of the compass linkage, thefirst transfer rod, and the second transfer rod are substantiallyparallel in order to maximize the effectiveness of the flight control.Furthermore, the first transfer rod extends along the pitch axis, thefirst transfer rod's longitudinal axis coinciding with said pitch axis,thereby enhancing the decoupling between the pitch and roll controls.

In contrast, by pivoting about the pitch axis, the root of the controlstick pushes or pulls the first branch that entrains the second branchof the compass linkage in rotation. Nevertheless, since the secondbranch is connected to the first transfer rod via a ball-jointpresenting a large amount of freedom in angular movements, the firsttransfer rod also lying on the same axis as the pitch axis, there is norisk of any coupling phenomenon appearing.

Furthermore, the flight control advantageously includes support meansfor the mechanical connection, the support means being firstly fastenedto the second branch and secondly secured to the pitch shaft.

More precisely, the support means are fastened to the second branch ofthe compass linkage via a hinge. Thus, when the pilot turns the controlstick about the roll axis, the root of the control stick moves the firstbranch, said first branch causing the second branch to turn about itsfastening points with the support means.

In addition, the support means are secured to the second end of thepitch shaft that passes through the second side face of the main anchorplatform. The support means are thus constrained to turn with the pitchshaft.

Finally, it is possible to envisage providing a secondary anchorplatform for anchoring the vertical transfer member to a structure ofthe aircraft in order to stabilize the flight control.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its advantages appear in greater detail from thefollowing description with embodiments given by way of illustration withreference to the accompanying figures, in which:

FIG. 1 is a diagrammatic view of the flight controls of a helicopter;

FIG. 2 is an isometric view of a first variant of a flight control;

FIG. 3 is a view showing the control stick connection pin; and

FIG. 4 is an isometric view of a second variant of a flight control.

Elements shown in more than one of the figures are given the samereferences in each of them.

MORE DETAILED DESCRIPTION

FIG. 1 is a diagrammatic view of the flight controls of an aircraft,more particularly of a helicopter.

Conventionally, the collective pitch lever 1 serves to modify thecollective pitch of the rotorcraft blades. The collective pitch lever 1is connected to a transfer lever 2 of a mixer 3 via an arm 4 and aconnected rod 5. When the collective pitch lever 1 is pulled upwards,the mixer 3 transfers this control to the left, right, and longitudinalservo-controls 6, 7, and 8. These servo-controls then move by the sameamount thus enabling the swashplate P to move upwards without tilting toincrease the pitch of the blades of the main rotor of the rotorcraft.When the collective pitch lever 1 is lowered, the movement is reversedand the pitch of the blades decreases.

The roll and pitch flight control comprises a control stick 9 forcontrol the swashplate P. When the control stick 9 is pushed forwards,the longitudinal servo-control 7 retracts via the longitudinal controlline, and the tilt lever L thereby tilting the swashplate P forwards.

On a rotorcraft provided with electric flight controls, the pitch leverand the pitch and roll flight control are electrically connected to theservo-controls 6, 7, and 8.

The invention provides an aircraft fitted with pitch and roll flightcontrol that is both compact and precise, without generating couplingbetween pitch and roll.

With reference to FIGS. 2 to 4, the pitch and roll flight control 10 ofthe invention comprises a control stick 11 provided in succession with ahandle 14, an intermediate segment 12, and a root 13.

By taking hold of the handle 14, the pilot can cause the control stick11 to turn about a pitch axis AXTANG and a roll axis AXROLL,respectively along arrows FTANG1, FTANG2, and FROLL1, FROLL2.

It should be observed that the pitch and roll axes AXTANG and AXROLL aremutually perpendicular.

In addition, the flight control 10 is provided with a pitch shaft 20 anda roll shaft 30 that are directed respectively along the pitch and rollaxes AXTANG and AXROLL. The pitch and roll shafts 20 and 30 are thusperpendicular to each other and substantially orthogonal to the controlstick 11.

The roll shaft 30 is connected by a mechanical connection 40 to the root13 of the control stick, while the pitch shaft 20 is pierced by thecontrol stick 11, the control stick 11 being directed substantiallyalong an elevation direction Z that is orthogonal to the pitch and rollaxes AXTANG and AXROLL.

Consequently, the pitch shaft 20 is pierced so as to present an oblongorifice 21 passing through the pitch shaft 20.

The control stick 11 then passes through the pitch shaft 20, and moreprecisely through the oblong orifice 21 of the pitch shaft 20.

In addition, the control stick 11 is constrained to turn with the pitchshaft 20 about the pitch axis AXTANG.

With reference to FIG. 3, a connection pin 70 enables such a connectionto be made.

The connection pin 70, fastened to the pitch shaft 20 in conventionalmanner, is arranged axially along the roll axis AXROLL. The longitudinalaxis of symmetry AXS of this connection pin 70, e.g. a cylindricalbarrel, therefore coincides with the roll axis AXROLL.

It can also be seen that the connection pin 70 passes through the oblongorifice 21, and naturally, the intermediate segment 12 of the controlstick 11.

Consequently, the control stick 11 can turn about the connection pin 70,and thus about the roll axis AXROLL, without generating mechanicalforces on the pitch shaft 20.

However, when the pilot pulls or pushes the control stick 11, theintermediate segment 12 and turns entrains the connection pin 70 andthus the pitch shaft 20. As explained below, by means of the mechanicalconnection 40, the control stick 11 does not generate mechanical forceson the roll axis, whatever the variant of the invention.

The pitch and roll flight control 10 thus enables pitch and roll to beeffectively decoupled.

For this purpose, the mechanical connection 40 implements a compasslinkage 41 having first and second branches 42 and 43. The first branch42 of the compass linkage 41 is also hinged firstly to the root 13 ofthe control stick, and secondly to the first end zone 43′ of the secondbranch 43, e.g. via a ball-joint connection.

In the first variant of the invention, shown diagrammatically in FIG. 2,the second end zone 43″ of the second branch 43 is fastened to the rollshaft 30.

Consequently, when the pilot acts on the control stick 11 to cause theaircraft to pitch, the root 13 of the control stick 11 pushes or pullsthe first branch of the compass linkage. The second branch 43 of thecompass linkage 41 then tilts relative to the roll shaft, withoutentraining the roll shaft to turn about the roll axis AXROLL.

In the second variant of the invention, shown in FIG. 4, the second endzone 43″ of the compass linkage is connected to the roll shaft 30 bytransfer means 44 of the mechanical connection 40, which transfer means44 are provided with a first transfer rod 45, an transfer member 46, anda second transfer rod 47.

Thus, the second branch 43″ of the compass linkage is hinged to thefirst transfer rod 45 via a ball-joint 48 presenting a large amount offreedom in movement, the first transfer rod 45 itself being hinged tothe transfer member 46. Finally, the transfer member 46 is connected tothe roll shaft 30 by the second transfer rod 47.

It should be observed that the first and second transfer rods 45 and 47are substantially horizontal and parallel to the pitch shaft 20, thefirst transfer rod 45 also being directed along the pitch axis AXTANGand having its own longitudinal axis of symmetry AXS′ coinciding withsaid pitch axis AXTANG. In contrast, the transfer member 46 issubstantially vertical and parallel to the control stick 11.

Thus, when the pilot moves the control stick along arrow FROLL1, theroot causes the second branch 43″ of the compass linkage 43 to moveangularly and consequently causes the first transfer rod 45 to movelinearly in a first direction F1.

The transfer member 46 then moves angularly and pushes the secondtransfer rod 47 in a second direction F2 opposite to the first directionF1. The roll shaft 30 then turns about the roll axis AXROLL asrepresented by arrow F3, i.e. in the same direction as the control stick11.

As mentioned above, this movement of the control stick has noconsequence for the pitch shaft 20 that remains in position.

Likewise, when the pilot tilts the control stick 11 about the pitch axisAXTANG, the control stick generates turning of the pitch shaft 20 viathe connection pin 70.

In contrast, the ball-joint 48 allows the second branch 43 of thecompass linkage 41 not to entrain rotation of the roll shaft 30.

In addition, the flight control includes support means 60 for the secondbranch 43 of the compass linkage 41.

These support means 60 are secured to the pitch shaft 20, and moreprecisely to the second end 20″ of the pitch shaft 20. In addition, thesupport means 60 are hinged to the second branch 43.

Thus, movement of the root 13 of the control stick 11 about the rollaxis AXROLL gives rise to turning of the second branch 43 of the compasslinkage about its hinge 61 to the support means 60.

In order to be properly secured on board the aircraft, the flightcontrol 10 optionally includes a main anchor platform 50 fastened underthe cockpit floor of the aircraft via its top face 53.

The second end 30″ of the roll shaft 30 is then hinged to a first sideface 51 of the main anchor platform 50. Since the first end 30′ of theroll shaft 30 is hinged to the structure of the aircraft, the roll shaft30 is properly secured.

Likewise, the second end 20″ of the pitch shaft 20 is hinged to a secondside face 52 of the main anchor platform 50, said second end 20″ of thepitch shaft 20 passing through the second side face 52. Since the firstend 20′ of the pitch shaft 20 is hinged to the structure of theaircraft, the pitch shaft 20 is properly secured.

It will be understood that the hinges of the pitch and roll shafts 20and 30 to the structure of the aircraft and to the main anchor platformare of conventional type and enable these pitch and roll shafts 20 and30 to perform rotary movement respectively about the pitch axis AXTANGand about the roll axis AXROLL under drive from the control stick 11.

Finally, the connection is optimized by fastening a secondary anchorplatform 49 both to the structure of the aircraft and to the transfermember 46, the transfer member 46 being capable of turning about itsfastener means 49′ fastening it to the secondary platform 49.

The control stick is thus compact, robust, and capable of decouplingpitch and roll controls.

In order to transmit these controls to the flight control members of theaircraft, e.g. the servo-controls 6, 7, and 8, the flight control 10includes a primary rod 22 hinged to a projection 21 on the pitch shaft20.

Similarly, it is provided with at least one secondary rod 32 hinged to aprojection 31 of the roll shaft, both secondary rods being visible inFIG. 4. The primary and secondary rods 22 and 32 can be mechanicallyconnected to the servo-controls for implementing control, e.g. via themixer 3.

Nevertheless, it is possible to implement flight controls that areelectric.

The flight control 10 then possesses a primary sensor 23 for sensing theposition of the pitch shaft 20, and at least one secondary sensor 33 forsensing the position of the roll shaft 30, these sensors being arrangedrespectively on the primary rod 22 and on the secondary rod 32 of thevariant shown in FIG. 4.

As shown in FIG. 4, it is possible for the sensors to be providedredundantly, e.g. by providing two secondary sensors 33 arrangedrespectively on first and second secondary rods.

The position sensors then send information to a control member relatingto the angular positions of the pitch and roll shafts 20 and 30, thecontrol member then adjusting the lengths of the servo-controls.

Naturally, the present invention can be subjected to numerous variantsin its implementation. Although several embodiments are described, itwill be understood that it is not conceivable to identify exhaustivelyall possible embodiments. It is naturally possible to envisage replacingany of the means described by equivalent means without going beyond theambit of the present invention.

1. An aircraft flight control (10) comprising a pitch and roll controlstick (11) suitable for being turned about a pitch axis (AXTANG) and aroll axis (AXROLL) that are mutually perpendicular, said control stick(11) being provided with a handle (14) and a root (13) interconnected byan intermediate segment (12) of said control stick (11), wherein theflight control (10) comprises a pitch shaft (20) and a roll shaft (30)that are mutually perpendicular for controlling the aircraft in pitchingand rolling by performing turning movements respectively about saidpitch and roll axes (AXTANG and AXROLL) under drive from said controlstick (11), said control stick (11) also passing through an oblongorifice (21) formed in said pitch shaft (20), said root (13) ismechanically connected to the roll shaft (30) by a mechanical connection(40) while said intermediate segment (12) is connected to the pitchshaft (20) by a connection pin (70) that passes through saidintermediate segment (12) and that is arranged axially in said oblongorifice (21).
 2. A flight control according to claim 1, wherein saidconnection pin is a bar (70) having said roll axis (AXROLL) as itslongitudinal axis of symmetry (AXS).
 3. A flight control according toclaim 1, wherein said flight control (10) comprises a main anchorplatform (50) anchoring it to said aircraft, and said roll and pitchshafts (20 and 30) are fastened to said main anchor platform (50) insuch a manner as to be capable of performing rotary movementsrespectively about said pitch and roll axes (AXTANG and AXROLL).
 4. Aflight control according to claim 1, including at least one primary rod(22) hinged on a primary projection (21) fastened to said pitch shaft(20).
 5. A flight control according to claim 1, that is provided with atleast one primary sensor (23) for sensing the position of said pitchshaft (20).
 6. A flight control according to claim 1, including at leastone secondary rod (32) hinged to a secondary projection (31) fastened tosaid roll shaft (30).
 7. A flight control according to claim 1, that isprovided with at least one secondary sensor (33) for sensing theposition of said pitch shaft (30).
 8. A flight control according toclaim 1, wherein said mechanical connection (40) includes a compasslinkage (41) provided with first and second branches (42, 43), saidfirst branch (42) being hinged to the root (13) of the control stick(11) and to a first end zone (43′) of the second branch (43).
 9. Aflight control according to claim 8, wherein a second end zone (43″) ofthe second branch (43) of the compass linkage (41) is hinged to the rollshaft (30).
 10. A flight control according to claim 8, wherein a secondend zone (43″) of the second branch (43) of the compass linkage (41) ismechanically connected to the roll shaft (30) via transfer means (44)comprising in succession a horizontal first transfer rod (45), avertical transfer member (46), followed by a horizontal second transferrod (47), a ball-joint (48) having a large amount of freedom in angularmovement being placed between said second branch (43) and said firsttransfer rod (45).
 11. A flight control according to claim 10, whereinsaid first transfer rod (45) extends along said pitch axis (AXTANG). 12.A flight control according to claim 10, wherein said ball-joint (48) canaccommodate a maximum amount of angular movement of plus or minus 20°.13. A flight control according to claim 10, including support means (60)for supporting the mechanical connection, said support means (60) beingfastened firstly to the second branch (43) and being secured secondly tothe pitch shaft (20).
 14. A flight control according to claim 10,including a secondary anchor platform (49) anchoring the verticaltransfer member (46) to a structure of the aircraft.